(a) Field of the Invention
The subject downhole combustion unit and process provides for injecting a high-temperature, high-pressure, thermal-energy carrier fluid, called herein “TECF”. The TECF is injected into either natural-occurring, permeable zones or propped-frac created permeable zones to create a desired, very large heating element in an underground surface area. This large, heating element surface area provides a means for economic, in-situ, pyrolysis, retorting, cracking and refining of a carbon-rich, geologic formation, which can be described as a fixed-bed, hydrocarbon formation, FBHF, or a fixed-bed, hydrocarbon deposit, FBHD. The FBHF and FBHD are defined as any carbon-rich geologic formation, including but not limited to those geologic formations containing deposits of kerogen, lignite/coal (including peat, lignite, brown coal, asphalt, bitumen, sub-bituminous coal, bituminous coal, anthracite coal), liquid petroleum, crude oil, depleted oil fields, heavy oil tar or gel-phase petroleum, and the like. The FBHF or FBHD of special, high-priority, economic development interest are the deposits of oil shale, tar sands, heavy-oil fields and lignite/coal beds.
(b) Discussion of Prior Art
Heretofore most designs for downhole combustion furnaces and processes are derived from surface operational models requiring clean exhaust gases with very low values of pollutants, such as unburned hydrocarbons, carbon monoxide and like gases. In the subject invention, the exhaust pollutants, from the downhole combustion chamber are commingled with other pollutants produced by the in-situ retorting process. Such pollutants must be extracted after being produced to the surface from the production wells. Consequently, the elaborate, pollutant-free combustion furnaces, with catalytic converters have no advantage, but many detriments for in-situ retorting applications.
None of the prior art patented methods and systems using compressed air and gas technology with boreholes have used a combustion unit as described herein for creating one or more large, thermal-energy heating elements in a permeable hydrocarbon zone. The heating elements extending outwardly from a well bore and conducting high volume rates of thermal-energy into a permeable, fixed-bed hydrocarbon deposit as discussed herein.